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Reduction of oxidized Rh catalysts under carbon monoxide (CO) exposure and reaction conditions were studied by using ambient-pressure x-ray photoelectron spectroscopy. First, Rh powders pressed into a pellet were deeply oxidized and the reduction process under 100 mTorr CO environment was monitored in situ at different temperatures. The oxidized Rh surfaces are composed of Rh2O3 and RhO2, the latter of which is more segregated near the surface. Both oxide species are reduced simultaneously to the metallic state; kinetic analyses indicate that the activation energy of the reduction of the Rh oxides is 1.68 eV, which is a little larger than those for Pd oxides, probably due to a stronger Rh–O interaction. Reduction of oxidized Rh nano-particles deposited on SiO2 under two reaction conditions (CO + O2 and CO + NO + O2) was observed with increasing temperature. It was found that the reduction temperature shifts to the higher temperature in the presence of NO, even though the S-factors are almost the same. The NO molecule more strongly prevents the reduction of oxidized Rh catalyst compared to O2.

Changes in Ti K-edge X-ray absorption fine structure (XAFS) spectra of lithium titanium oxide (LTO) during the charge discharge cycle of lithium ion battery were investigated by using a specially designed cell for in situ X-ray measurement. Thought LTO is famous for zero-strain lattice during the charge/discharge cycle, the significant spectral changes might be attributed to Li migration in the lattice. The experimental results were compared with the theoretical simulation, and the spectral changes were caused both by the slight changes in oxygen position parameter that affected titanium neighbors and Li migration.

The charging effect often complicates photoemission spectroscopy and x-ray absorption spectroscopy of an insulating material. Here, monolayer graphene was used as a conductive layer to prevent the charging effect of insulating substrates such as glass and LiNbO3. Charging-free spectra were obtained with various photon energies ranging from vacuum ultraviolet light to hard x-rays. This method could also be applied to photoemission spectroscopy of epoxy adhesives and to photoemission electron microscopy of an insulating film. Photoelectron transmissivities for the transferred graphene film were evaluated over a wide kinetic energy range from 29 to 7910 eV. A minimum transmissivity of ∼0.1 was found at a kinetic energy of ∼60 eV, which rose to 0.86 at 7910 eV. In terms of the kinetic energy dependence of the transmissivity, this method is especially suitable for conventional and hard x-ray photoelectron spectroscopy.

A novel, highly active three-way catalyst, rhodium supported on Y- and La-added zirconia (Rh/Zr–Y–La–O), was found in this study. Rh/Zr–Y–La–O showed superior performance to a previously reported Rh on La-added ZrO2 (Rh/Zr–La–O) catalyst (Kawabata et al., Chem. Commun., 2013, 49(38), 4015; Catal. Sci. Technol. 2014, 4(3), 697).21,22 The effects of Y addition to ZrO2-based supports were investigated in detail. CO temperature-programmed reduction and in situ Fourier transform infrared spectra of adsorbed NO species indicated that Y addition to La-containing ZrO2 enhanced the reducibility of rhodium supported on the catalyst and that more metallic Rh was exposed on the surface after the oxidation of Rh/Zr–Y–La–O than of Rh/Zr–La–O. Before and after an aging treatment at 1273 K that simulated 80 000 km travelled by vehicles, Rh/Zr–Y–La–O showed high steam reforming activity. After the aging treatment, Rh/Zr–Y–La–O was deactivated using an oxidation treatment, but its three-way catalysis activity was completely regenerated after a short (5 min) exposure to steam reforming reaction conditions, demonstrating self-regeneration capability. After the aging treatment, Rh/Zr–Y–La–O showed higher rhodium dispersion than other catalysts. This was attributed to the high surface area of the support after aging and the stabilization of ZrO2 by the addition of Y. Our findings highlight the role of catalyst supports in designing effective three-way catalysts with high tolerance to the oxidative conditions in new vehicles and engines.

酸素貯蔵材(OSC)に貴金属を担持した触媒において，白金(Pt)とロジウム(Rh)の担持状態や触媒特性に及ぼす影響を，酸化セリウム(CeO2)，セリウム-ジルコニウム(Ce–Zr)複酸化物，セリウム-プラセオジム(Ce–Pr)複酸化物および酸化プラセオジム(Pr6O11)を用いて調べた．TPR結果から，Prを含んだOSCを担体にしたPt–Rh/Ce–Pr複酸化物とPt–Rh/Pr6O11の触媒は優れた酸素放出特性や水素(H2)の貯蔵特性を示した．これらの触媒は，他の二つの触媒と比べて，H2や一酸化炭素(CO)を還元剤にした一酸化窒素(NO)浄化反応に高い活性を発現することがわかった． XPS分析結果から，Pt–Rh/Ce–Pr複酸化物とPt–Rh/Pr6O11のPt表面はCeO2，Ce–Zr複酸化物に担持されたものと異なり，電子密度が希薄な状態である．EXAFS分析結果から，PtとRhは合金化しており，Pt–Rh/Ce–Pr複酸化物とPt–Rh/Pr6O11のRhはCeO2，Ce–Zr複酸化物に担持されたものに比べて金属に近い還元状態であることがわかった． 以上のことから，貴金属の担持状態や優れた触媒特性は，担体であるOSCとの強い相互作用に起因すると推察した．

Optical and structural properties of rare-earth free and pure Mg thin film coated with Pd have been investigated. Optical examination indicates that the fully hydrogenated films are in a color-neutral transparent state. With increasing temperature up to 453 K in air, nontransparent scratch-like parts that correspond to dehydrogenated Mg precipitate in macroscopic scale, and their number gradually increases and grows sharply along specific orientations. The structural characterization indicates that the Mg layer is composed of epitaxial columnar grains whose widths are less than 100 nm with a c -axis preferred orientation for the Mg layer. The columnar grains are restructured to grains with 50–100 nm diameter during hydrogenation–dehydrogenation (optical switching) cycles.

MgNiC x with an amorphous structure were synthesized up to x =1.31 by mechanical alloying of amorphous (a-)MgNi and graphite as starting materials. The core-level X-ray photoelectron spectroscopy revealed that the original bonding states with metallic character of a-MgNi remained even in the sample with high carbon content although the graphite dissolved as interstitial carbon and it mainly bounded with Mg in a-MgNi. The crystallization temperature of MgNiC x increased with increasing carbon content up to x =0.85, which was accompanied by a drastic change in the crystallization processes. Upon hydrogenation of MgNiC x , the atomic ratio of hydrogen plus carbon to metal (H+C)/M remained a constant value of ≃0.9 through the whole system, indicating that carbon atoms dissolved into the sites that otherwise would have been occupied by hydrogen atoms.

自動車排出ガス浄化用Pd系触媒において, 助触媒である酸素貯蔵剤 (Oxygen Storage Component : OSC) が, 熱エージング後のNOx浄化特性へ及ぼす影響をCeO2とCeZr複合酸化物を用いて, 触媒の構造, 状態, 酸素貯蔵能 (OSC能) , NO吸着特性の点から解析した.CeO2へZrを添加することにより, CeO2と比較して熱エージング後もOSC能が維持され, NOx浄化性能も向上した. 種々の解析結果より, これは, 以前から報告されているZr添加によるシンタリング抑制効果のほかに, CeZr複合酸化物には立方晶系構造と正方晶系構造の2相が存在し, このうちの正方晶系構造を持つ相が酸素の吸蔵, 放出を促進する効果があると考察した. その結果助触媒としてCeZr複合酸化物を用いると, 自動車排ガスのように酸素濃度が変動する雰囲気においても, 活性種に吸着した酸素がOSCへスピルオーバーし活性種の還元状態を維持できるので, NOを吸着, 浄化できるものと推察した.

酸化セリウムを酸素貯蔵材として使用したパラジウム担持触媒の二酸化硫黄 (SO2) ガスによる被毒現象を検討した. 還元雰囲気下において, 酸化セリウムに担持したパラジウムに吸着した硫黄の脱離温度は, 酸化アルミニウムに比較して高温化しており, 被毒状態からの触媒活性の回復に影響を与えていることが判明した. この高温化は, 吸着した硫黄量と触媒の状態変化の解析から, 還元されたパラジウムと酸化セリウム間における酸化セリウムの還元性に基づく栢互作用が原因であると推察された. また, 573Kにおける, パラジウム担持酸化セリウムのSO2被毒に対する酸化, 還元雰囲気の影響を検討した結果, 酸化雰囲気では, SO2の吸着が酸化セリウムの酸素貯蔵を阻害し, 還元雰囲気では, パラジウム表面を不活性化しているものと推論した.

Rhodium on a La-containing ZrO2 support effectively eliminated NOx from a synthetic auto exhaust gas under fluctuating oxygen conditions. Rhodium particles maintained a low oxidation state on the ZrO2–La2O3 mixed oxide even after treatment with 5% O2 at 773 K, highlighting the significant effect of the La addition.

Highly dispersive and size controlled Pd and Pt nanoclusters have been synthesized by gas condensation and Arc plasma source. The morphology, crystallographic structures, electronic structure and the temperature dependence of chemical states of nanocluster were investigated by using TEM, AFM, EXAFS and XPS, respectively. The results show that non-passivized Pd nanoclusters with the size of 1.5~ 5.7nm are consisted with pure Pd core covered by highly oxidized PdO2 thin layer. The dioxide state PdO2 layers start to converting to Pd at 120°C and vanishing at 180°C in a reduction atmosphere.

Rhodium supported on lanthanoid (La, Ce, Pr, or Nd)-containing ZrO2 was investigated as a three-way catalyst following an aging treatment (oxidation at 1273 K) that simulates 80000 km of mileage in real vehicles. The properties of rhodium were assessed by transmission electron microscopy, CO chemisorption, and temperature-programmed reduction using CO. The oxidation states of rhodium before and after the aging treatment were evaluated using X-ray photoelectron spectroscopy. Rhodium supported on lanthanum-containing ZrO2 (Rh/Zr–La–O) was highly active for the removal of NOx and hydrocarbons from a synthetic auto exhaust. The support determined the oxidation state of rhodium after the aging treatment: rhodium supported on Zr–La–O maintained its low oxidation state during the three-way catalytic reaction and after the aging treatment, whereas rhodium supported on ZrO2 and other lanthanoid-containing ZrO2 was converted to the higher oxidation states. The Rh/Zr–La–O catalyst, following the aging treatment, exhibited superior activity for the steam reforming reaction. The hydrogen produced from the steam reforming reaction reduced the previously oxidized Rh in Rh/Zr–La–O, thereby regenerating the catalyst that was previously deactivated by an oxidation treatment. Self-regeneration of the Rh/Zr–La–O catalyst by the steam reforming reaction was more efficient when compared with that of the other lanthanoid-containing ZrO2 catalysts. These results highlight the potential of the present strategy for developing active three-way catalysts with high tolerance to oxidative conditions.

Systematic investigation of the influence of vacuum ultraviolet (VUV) irradiation on the valence degeneration in a Sm over-layer on a HOPG substrate was performed using in-situ photoemission spectroscopy (XPS, UPS, and ARPES) for the Sm coverage regime of 0.05-3.6 A. This investigation confirmed that VUV irradiation-induced degeneration of divalent Sm exerts a more profound effect than Sm contamination during photoemission spectroscopy even under UHV. We found that the charge transfer occurs mainly from divalent Sm to the HOPG surface.